It is known that embroideries can be executed by means of a sewing machine, wherein the embroidery is stored in a memory that contains stitch data for the embroidery. An operator selects, for example, an embroidery from the memory and places a sewing material, on which the embroidery is to be executed, stretched or clamped onto an embroidery hoop [hereinafter referred to as “hoop” only] which is arranged in the sewing machine in such a way that a control program for the sewing machine mechanically moves the hoop in accordance with a control program and stitch data when executing the embroidery on the sewing material. The sewing material is usually a fabric, which concept will be used hereinafter as an example to designate all types of sewing materials.
When embroidering or sewing on a fabric in a sewing machine, it is common practice to start the embroidery or the seam from a certain desired position. Thus, it may, for example, be desirable for the first stitch in the embroidery or the seam to start from a feature which already exists on the fabric. Such a feature may consist of an already existing embroidery element, a certain seam, a certain ornamental element such as a pearl, a print, etc. Positioning the embroidery or seam in question in such a desired position may be difficult, especially if such an adaptation is desired with very high precision. If an operator wishes to correctly place, for example, an embroidery element on a fabric to a specific position, this may be done by carefully moving the fabric being clamped in a hoop, and during the whole sewing process manually actively synchronize the position of the fabric with a corresponding position in the processor of the sewing machine. Other issues of interest when using a hoop is, e.g. for a user to have an idea about how parts of an embroidery are related to each other.
A drawback in the use of sewing machines provided with a display is that no method and adherent devices exist to show on the display an undistorted picture of the full work area such as, for example, the work area of a fabric clamped in a hoop. As will be understood from the description below such assistance would be a valuable support in performing different applications on a sewing machine of the kind.
One solution to the difficulty of correct positioning is shown in document DE 19921130. The document discloses a method in which an embroidery is to be placed at a given position on a fabric. The fabric wears machine-readable symbols which indicate where the embroidery is to be placed. Each such symbol is detected by a sensor that performs readings, where these readings are transformed into position data which are used by the sewing machine for placing the embroidery pattern at the given place. The fabric is initially provided with printing containing said symbols. The symbols contain an optical fluorescent material. The sensor is a light-detecting scanner. A disadvantage of such a method is that it cannot, of course, be used on fabrics that have not been provided initially with pre-print containing position determinations.
Machine vision is a field of technology that is being increasingly used in industry and which also starts to be used in certain consumer products. This means that images are captured with a camera, to which image-processing algorithms are then applied in order to obtain certain desired information, often as to where an object is situated, if it has the correct appearance, how many objects there are, etc.
A machine vision system is disclosed in document US 2006/0015209. Said document discusses the use of a camera in a sewing machine to ensure a problem-free operation of the sewing machine. This is solved by utilizing a camera for monitoring sewing machine elements and thereby assist a user with respect to the proper use of sewing machine elements.